The "purge" command:

The purge command removes content from a repository and stores that content
in a "graveyard". The graveyard exists so that content can be recovered
using the "fossil purge undo" command. The "fossil purge obliterate"
command empties the graveyard, making the content unrecoverable.
==== WARNING: This command can potentially destroy historical data and ====
==== leave your repository in a goofy state. Know what you are doing! ====
==== Make a backup of your repository before using this command! ====
==== FURTHER WARNING: This command is a work-in-progress and may yet ====
==== contain bugs. ====
fossil purge artifacts UUID... ?OPTIONS?
Move arbitrary artifacts identified by the UUID list into the
graveyard.
fossil purge cat UUID...
Write the content of one or more artifacts in the graveyard onto
standard output.
fossil purge checkins TAGS... ?OPTIONS?
Move the check-ins or branches identified by TAGS and all of
their descendants out of the repository and into the graveyard.
If TAGS includes a branch name then it means all the check-ins
on the most recent occurrence of that branch.
fossil purge files NAME ... ?OPTIONS?
Move all instances of files called NAME into the graveyard.
NAME should be the name of the file relative to the root of the
repository. If NAME is a directory, then all files within that
directory are moved.
fossil purge list|ls ?-l?
Show the graveyard of prior purges. The -l option gives more
detail in the output.
fossil purge obliterate ID... ?--force?
Remove one or more purge events from the graveyard. Once a purge
event is obliterated, it can no longer be undone. The --force
option suppresses the confirmation prompt.
fossil purge tickets NAME ... ?OPTIONS?
TBD...
fossil purge undo ID
Restore the content previously removed by purge ID.
fossil purge wiki NAME ... ?OPTIONS?
TBD...
COMMON OPTIONS:
--explain Make no changes, but show what would happen.
--dry-run An alias for --explain
SUMMARY:
fossil purge artifacts UUID.. [OPTIONS]
fossil purge cat UUID...
fossil purge checkins TAGS... [OPTIONS]
fossil purge files FILENAME... [OPTIONS]
fossil purge list
fossil purge obliterate ID...
fossil purge tickets NAME... [OPTIONS]
fossil purge undo ID
fossil purge wiki NAME... [OPTIONS]